The present invention relates to a thermal transfer color recording apparatus in which recording is performed by thermally transferring the color ink of a transfer sheet to a recording medium, and, more particularly, to a thermal transfer color recording apparatus and recording method which transfer and record a plurality of colors in register.
As disclosed in, for example, the official gazette of Japanese Patent Application Laid-Open Application No. 59-42976, a prior-art thermal transfer color recording apparatus comprises recording paper, and a transfer film having a base is divided into color zones coated with inks in a plurality of colors. At the time of a recording operation, in a recording portion composed of a thermal head and a platen roller, the transfer film and the recording paper, placed one over the other with the region of the first color of the former opposed to the latter, are conveyed in a forward direction, and the thermal head is actuated in response to a picture recording signal corresponding to the first color, thereby to transfer and record the first color. After the transfer recording of the first color, only the recording paper is conveyed in a reverse direction to a record starting position, and the transfer film and the recording paper, placed one over the other with the region of the second color of the former opposed to the latter, are conveyed in the forward direction again, thereby to transfer and record the second color. These operations are thereafter repeated to transfer the plurality of colors in register, whereby the color recording is carried out.
In such color recording, the transfer of the color ink is effected only when the recording paper is conveyed in the forward direction. Therefore, each time one color is transferred and recorded, the recording paper must be conveyed in the reverse direction to the record starting position.
In this manner, at the transfer recording operation, the recording paper is conveyed in the forward direction while being depressed against the platen roller by the thermal head along with the transfer film. In contrast, at a returning operation, the recording paper is conveyed in the reverse direction by the platen roller without being depressed by the thermal head.
Accordingly, the recording paper undergoes a feed error due to the difference of the magnitudes of deformation and slip of the platen roller at the times of the forward conveyance and the reverse conveyance. For this reason, it is difficult to locate the recording paper to the record starting position by the reverse conveyance thereof, and clear color picture recording is difficult.
Additionally, in such color recording, a period of time for conveying the recording paper in the reverse direction, apart from the positioning conveyance of the transfer film, is required separately from a recording period of time. This leads to the problem that shortening the recording period of time is difficult.
An object of the present invention is to provide a thermal transfer color recording apparatus and recording method in which a plurality of colors can be recorded on a recording medium in register at a high register recording position accuracy.
A thermal transfer color recording apparatus according to the present invention comprises a transfer sheet in which a plurality of types of color inks, adapted to be thermally transferred, are arrayed on a large number of different regions of a base thereof, and a thermal head in which a plurality of heat generating elements, adapted to generate heat in response to a picture recording signal, are disposed in the form of a line. When a picture is recorded, the transfer sheet and a recording medium, placed one over the other, are conveyed a forward direction or a reverse direction by a platen roller while being depressed by the thermal head actuated in response to the picture recording signal. Further, only the transfer sheet can be conveyed by conveyance means.
In this manner, the platen roller rotates forwardly or reversely under the pressure of the thermal head so as to convey the transfer sheet and the recording medium the forward or reverse direction. Since the pressures of the thermal head in both the forward and reverse conveying directions are equal and remain unchanged, the platen roller does not undergo any difference in the magnitudes of deformation during the conveying operations in both the directions.